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Recent Accounting Pronouncements and Changes to Accounting Policies - Schedule of Impact of Changes to Accounting Policies on Retained Earnings (Detail) - Retained earnings [member] - Increase (decrease) due to application of IFRS 15 [member] $ in Millions | Jan. 01, 2018 CAD ($)
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Disclosure of expected impact of initial application of new standards or interpretations [line items] |
Total impact of change in accounting policy | $ (23.9)
Continuing operations [member] | Change Orders and Claims [Member] |
Disclosure of expected impact of initial application of new standards or interpretations [line items] |
Total impact of change in accounting policy | (3.0)
Continuing operations [member] | Significant Financing Component [Member] |
Disclosure of expected impact of initial application of new standards or interpretations [line items] |
Total impact of change in accounting policy | 1.7
Discontinued operations [member] | Construction Services [member] |
Disclosure of expected impact of initial application of new standards or interpretations [line items] |
Total impact of change in accounting policy | $ (22.6)

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